In　this　work,　the　efficient　capture　of　dichloromethane　(DCM)　with　ionic　liquids　(ILs)　was　proposed　and　systematically　investigated.　The　carboxylic　acid-based　anion　and　quaternary　phosphonium　cation　were　screened　out,　and　on　this　basis　the　designed　tetrabutylphosphonium　hexanoate　([P4444][C5COO])　and　tetrabutylammonium　hexanoate　([N4444][C5COO])　ILs　were　finally　synthesized.　The　results　demonstrate　that　[P4444][C5COO]　exhibits　the　optimal　absorption　performance　(1400　mg　center　dot　g　�　1　at　30　degrees　C　and　0.3　bar).　Notably,　the　Henry＇s　law　constant　for　DCM　in　[P4444][C5COO]　(3.02　Pa　center　dot　m3　center　dot　mol-　1　at　25　degrees　C)　is　the　lowest　among　all　solvents　documented　in　the　literature.　The　microscopic　mechanism　was　explored　by　1H　NMR　spectra,　quantum　chemical　(QC)　calculations　and　molecular　dynamics　(MD)　simulations.　The　results　suggest　that　anion　plays　a　dominant　role,　while　weak　cation-anion　interaction　and　large　free　volume　of　cations　are　conducive　to　the　absorption　of　DCM.　The　proposed　IL　was　considered　as　a　promising　alternative　absorbent　to　achieve　high　absorption　capacity,　suitable　physicochemical　properties　and　excellent　recyclability.